cursing you for a lifetime

The next event had a massive influence on the proceeding story line. In the fight between Sasuke and Orochimaru after Sasuke had found his strength and will power again, something unpredictable and inconceivable took place: Sasuke had been cursed by Orochimaru.
Not only that Sasuke passed out under heavy pains and Sakura was left alone with the two unconscious boys (Naruto didn't wake up since Orochimaru seemed to have sealed his Kyuubi power), but this seal also turned out to be extremely dangerous afterwards and should leave not only scars behind..

We soon should get to know that while being possesed by this curse, Sasuke doesn't act as himself anymore, which was proven in the battle against the 3 Sound ninjas. Sasuke was completely out of his mind and to some point, really frightening. Orochimaru told Sasuke that if he wanted power, he would seek him for sure - and unfortunately, he was right. From that moment on, whenever Sasuke was in need of strength, the seal started to take him over - at first he fought against it, but soon Sasuke didn't have any choice left.

After finally having found the way out of the forest of death with the help of Kabuto, the next inquiry was already waiting for them. Before the next tournament started though, Sakura worried about Sasuke's shape and wanted him to stay out of the Chuunin exam; Naruto who was at first only irritated because of Sasuke's weird behaviour, changed his mind after the following words:

"Naruto.. I also want to fight you here."
Sasuke, Chapter 48

Naruto was shocked and innerly probably incredibly glad and relieved at the same time, since those were the first words Sasuke had used to acknowledge him. During the time with Team Seven, Sasuke must have already seen what hidden power slumbers within Naruto and both of them were now only waiting for their turn, to point out who really is the stronger one once and for all.

However, unfortunately, fate decided to have its own will once more, and Sasuke was the first one chosen in battle. He was to fight against one of Orochimaru's henchmen and to say so much - it didn't look too good at all at the beginning. But after Naruto had cheered for Sasuke loudly as always and once he had seen him on the tribune, Sasuke rememberd his fight with with Lee. Thus he had the idea of copying one of the moves Lee had used on him during the fight at the beginning of the Chuunin exam, which was really incredible, when one thinks about it. After all, Lee had to train hours and days for completing this move while Sasuke was able to analyse it in such a short time!

He won the fight and left together with Kakashi the tournament, to take a closer look at the sign which almost took possesion of Sasuke again, but especially to Orochimaru's surprise (who watched from nearby, disguised) he fought it back thanks to his strong will.

Even as the story progressed, the words Sasuke had told Naruto earlier should get a special place in Naruto's mind for a lifetime. After all, his long time rival, the person he aspired since he could possibly think, stated more or less his recognition for him.
Naruto wasn't even able to answer properly at that time, but not too long after, Naruto was aware of his feelings and also told Sasuke that he also couldn't wait to fight him. Both boys had a determinded look on their faces and one could almost feel the tension in the air.

Found at Chapter 14, Episode 8